Magnetic hard disk drives are an essential part of the modern personal computer, such drives being used to store large amounts of data in digital form. It is possible but unusual to change the hard drive of a personal computer, but when such a change is effected the computer has in general be powered down before the drive can safely be removed and new drive inserted in order not to cause damage to the drive. This is usually not a problem as shutting down computer and restarting it is relatively rapid compared with the time it takes to place the hard drive itself.
Magnetic hard drives do, however, have other uses then as memory devices for personal computers. In particular, they can be used as storage media for large amounts of data because of their large capacity combined with the speed with which such data can be recorded. In some applications, a plurality of such drives are used for the simultaneous recording of data.
As will be appreciated, although hard disk drives can store very large amounts of data, for example 10 Gb or more, there comes a time when they are full to capacity and need to be changed for empty drives. However, this causes problems when continuous data recording is required because it is then impossible to power down the whole data recording system.
An approach to this problem has been to locate each hard disk drive in a carrier which in turn is locked in place in a suitable slot in the data reporter, the drive making electrical connection with the rest of the recording system through a suitable plug and socket. The plug and socket enable the necessary electrical connections to be made, and the lock which can be used to lock the carrier in the slot and prevent its removal, activates a switch which controls the electrical power to the hard drive. Thus, when the lock is unlocked, thereby enabling the carrier and hard drive to be inserted and removed, power to the drive has been disconnected and the drive can be safely inserted or removed, However, locking the lock both serves to prevent the carrier and associated drive from being removed, and it also applies power to drive via a switch which is activated in the process of locking the lock.
Whilst the interlock on the power supply to the individual hard drives usual is that the drives can be replaced without damage to the ensures that the drives can be replaced without damage to the drives and/or other devices in the data recorders caused, for example, by breaking one or more connections between them prior to the drive being powered down, it does not remove the problem of in some cases of having to replace the large number of drives at the same time. Furthermore, when multiple drive changes are effected, it is usually important to identify which drive was located in which slot for the data recorder because particular slots in these recorders are often used to record data of a particular type or from a particular source. Labels could be used to identify individual carriers, but with relatively large numbers having to changed at one time, and the large number of replacements, it becomes difficult to monitor the situation.
One possible solution to the problem would be to mount a plurality of hard disk drives in a single carrier and thereby enable all or the drives in the carrier to be replaced in a single operation, power to be drives then being controlled by a locking mechanism in a similar manner to that used hitherto for carriers holding a single hard drive. Unfortunately, a new problem is then encountered due to the high insertion and withdrawal forces required to connect and disconnected plug and socket connectors of the individual drives which typically involve making and breaking eighty connections each. Data recorders recording simultaneously on eight hard drives would then require such large forces to plug and unplug all eight connections simultaneously that doing so is either physically impossible by hand or it results in damage to the equipment itself.
A solution to the problem of high insertion force for a multiplicity of connectors would be to use a so-called zero insertion force connector, such connectors being available with several hundred connections. However, zero insertion force connectors do not make all of their contacts simultaneously, and electrical damage could occur if they were used to connect a plurality of hard disk drives in carrier into a data recorder because the power supply to the drives could stay on after or be switched on before other connections are broken or made.